Ryukyu Awamori is thought to get its name from the bubbles awa (泡) that rise and swell mori (盛) during its distillation. Okinawans have refined the distillation process by incorporating techniques from nearby countries and making it more suitable for their subtropical climate along the way, including by introducing koji mold. Kusu (古酒, "old liquor") Awamoris aged in clay pots for 20 years or more prior to bottling have a sweet vanilla-like aroma and an unparalleled smoothness of taste considering their high alcohol content.